drbd: Removed a race that could cause unexpected execution of w_make_resync_request()

The actual race happened int the drbd_start_resync() function. Where
drbd_resync_finished() -> __drbd_set_state() set STOP_SYNC_TIMER and
armed the timer.

If the timer fired before execution reaches the mod_timer statement
at the end of drbd_start_resync() the latter would cause an
unexpected call to w_make_resync_request().

Removed the STOP_SYNC_TIMER bit, and base it on the connection state.

The STOP_SYNC_TIMER bit probably originates probably the time before
the state engine.

Signed-off-by: Philipp Reisner <philipp.reisner@linbit.com>
Signed-off-by: Lars Ellenberg <lars.ellenberg@linbit.com>

1 files changed, 2 insertions, 16 deletions

diff --git a/drivers/block/drbd/drbd_main.c b/drivers/block/drbd/drbd_main.c
index 73c905d0ef18..5dd071e5c921 100644
--- a/drivers/block/drbd/drbd_main.c
+++ b/drivers/block/drbd/drbd_main.c
@@ -1052,12 +1052,6 @@ int __drbd_set_state(struct drbd_conf *mdev,
         wake_up(&mdev->misc_wait);
         wake_up(&mdev->state_wait);
 
-        /*   post-state-change actions   */
-        if (os.conn >= C_SYNC_SOURCE   && ns.conn <= C_CONNECTED) {
-                set_bit(STOP_SYNC_TIMER, &mdev->flags);
-                mod_timer(&mdev->resync_timer, jiffies);
-        }
-
         /* aborted verify run. log the last position */
         if ((os.conn == C_VERIFY_S || os.conn == C_VERIFY_T) &&
             ns.conn < C_CONNECTED) {
@@ -1072,22 +1066,14 @@ int __drbd_set_state(struct drbd_conf *mdev,
                 dev_info(DEV, "Syncer continues.\n");
                 mdev->rs_paused += (long)jiffies
                                   -(long)mdev->rs_mark_time[mdev->rs_last_mark];
-                if (ns.conn == C_SYNC_TARGET) {
-                        if (!test_and_clear_bit(STOP_SYNC_TIMER, &mdev->flags))
-                                mod_timer(&mdev->resync_timer, jiffies);
-                        /* This if (!test_bit) is only needed for the case
-                           that a device that has ceased to used its timer,
-                           i.e. it is already in drbd_resync_finished() gets
-                           paused and resumed. */
-                }
+                if (ns.conn == C_SYNC_TARGET)
+                        mod_timer(&mdev->resync_timer, jiffies);
         }
 
         if ((os.conn == C_SYNC_TARGET  || os.conn == C_SYNC_SOURCE) &&
             (ns.conn == C_PAUSED_SYNC_T || ns.conn == C_PAUSED_SYNC_S)) {
                 dev_info(DEV, "Resync suspended\n");
                 mdev->rs_mark_time[mdev->rs_last_mark] = jiffies;
-                if (ns.conn == C_PAUSED_SYNC_T)
-                        set_bit(STOP_SYNC_TIMER, &mdev->flags);
         }
 
         if (os.conn == C_CONNECTED &&